soc: arm: stm32wba: add support for standby mode with ram retention

Add support for STM32WBA Standby low-power mode with RAM retention.

Signed-off-by: Guillaume Gautier <guillaume.gautier-ext@st.com>

soc/arm/st_stm32/stm32wba/Kconfig.defconfig.series

@@ -39,4 +39,26 @@ config ENTROPY_STM32_CLK_CHECK
 
 endif
 
+if PM_S2RAM
+
+config COUNTER
+	default y
+
+config COUNTER_RTC_STM32_SUBSECONDS
+	default y
+
+config STM32_LPTIM_STDBY_TIMER
+	default y
+
+config TICKLESS_KERNEL
+	default y
+
+config COUNTER_RTC_STM32_SAVE_VALUE_BETWEEN_RESETS
+	default y
+
+config IDLE_STACK_SIZE
+	default 512
+
+endif
+
 endif # SOC_SERIES_STM32WBAX

soc/arm/st_stm32/stm32wba/power.c

@@ -7,6 +7,8 @@
 #include <zephyr/pm/pm.h>
 #include <soc.h>
 #include <zephyr/init.h>
+#include <zephyr/arch/common/pm_s2ram.h>
+#include <zephyr/drivers/timer/system_timer.h>
 
 #include <stm32wbaxx_ll_bus.h>
 #include <stm32wbaxx_ll_cortex.h>
@@ -24,7 +26,25 @@
 
 LOG_MODULE_DECLARE(soc, CONFIG_SOC_LOG_LEVEL);
 
-void set_mode_stop(uint8_t substate_id)
+static int stm32_power_init(void);
+
+static void disable_cache(void)
+{
+	/* Disabling ICACHE */
+	LL_ICACHE_Disable();
+	while (LL_ICACHE_IsEnabled() == 1U) {
+	}
+
+	/* Wait until ICACHE_SR.BUSYF is cleared */
+	while (LL_ICACHE_IsActiveFlag_BUSY() == 1U) {
+	}
+
+	/* Wait until ICACHE_SR.BSYENDF is set */
+	while (LL_ICACHE_IsActiveFlag_BSYEND() == 0U) {
+	}
+}
+
+static void set_mode_stop(uint8_t substate_id)
 {
 
 	LL_PWR_ClearFlag_STOP();
@@ -33,10 +53,7 @@ void set_mode_stop(uint8_t substate_id)
 	/* Erratum 2.2.15:
 	 * Disabling ICACHE is required before entering stop mode
 	 */
-	LL_ICACHE_Disable();
+	disable_cache();
-	while (LL_ICACHE_IsEnabled() == 1U) {
-	}
-
 
 #ifdef CONFIG_BT_STM32WBA
 	scm_setwaitstates(LP);
@@ -60,35 +77,76 @@ void set_mode_stop(uint8_t substate_id)
 	}
 }
 
+#if defined(CONFIG_PM_S2RAM)
+static int suspend_to_ram(void)
+{
+	LL_LPM_EnableDeepSleep();
+
+	while (LL_PWR_IsActiveFlag_ACTVOS() == 0) {
+	}
+
+	/* Select mode entry : WFE or WFI and enter the CPU selected mode */
+	k_cpu_idle();
+
+	return 0;
+}
+
+static void set_mode_suspend_to_ram(void)
+{
+	/* Enable SRAM full retention */
+	LL_PWR_SetSRAM1SBRetention(LL_PWR_SRAM1_SB_FULL_RETENTION);
+	LL_PWR_SetSRAM2SBRetention(LL_PWR_SRAM2_SB_FULL_RETENTION);
+
+	/* Enable RTC wakeup
+	 * This configures an internal pin that generates an event to wakeup the system
+	 */
+	LL_PWR_EnableWakeUpPin(LL_PWR_WAKEUP_PIN7);
+	LL_PWR_SetWakeUpPinSignal3Selection(LL_PWR_WAKEUP_PIN7);
+
+	/* Clear flags */
+	LL_PWR_ClearFlag_SB();
+	LL_PWR_ClearFlag_WU();
+	LL_RCC_ClearResetFlags();
+
+	disable_cache();
+
+	/* Select standby mode */
+	LL_PWR_SetPowerMode(LL_PWR_MODE_STANDBY);
+
+	/* Save context and enter Standby mode */
+	arch_pm_s2ram_suspend(suspend_to_ram);
+
+	/* Execution is restored at this point after wake up */
+	/* Restore system clock as soon as we exit standby mode */
+	sys_clock_idle_exit();
+}
+#endif
+
 /* Invoke Low Power/System Off specific Tasks */
 void pm_state_set(enum pm_state state, uint8_t substate_id)
 {
 	switch (state) {
 	case PM_STATE_SUSPEND_TO_IDLE:
 		set_mode_stop(substate_id);
+
+		/* Select mode entry : WFE or WFI and enter the CPU selected mode */
+		k_cpu_idle();
+
 		break;
-	case PM_STATE_STANDBY:
+#if defined(CONFIG_PM_S2RAM)
-		/* Not supported today */
+	case PM_STATE_SUSPEND_TO_RAM:
-		__fallthrough;
+		set_mode_suspend_to_ram();
+		break;
+#endif
 	default:
 		LOG_DBG("Unsupported power state %u", state);
 		return;
 	}
-
-	/* Select mode entry : WFE or WFI and enter the CPU selected mode */
-	k_cpu_idle();
 }
 
 /* Handle SOC specific activity after Low Power Mode Exit */
 void pm_state_exit_post_ops(enum pm_state state, uint8_t substate_id)
 {
-	/* Erratum 2.2.15:
-	 * Enable ICACHE when exiting stop mode
-	 */
-	LL_ICACHE_Enable();
-	while (LL_ICACHE_IsEnabled() == 0U) {
-	}
-
 #ifdef CONFIG_BT_STM32WBA
 	if (LL_PWR_IsActiveFlag_STOP() == 1U) {
 		scm_setup();
@@ -100,16 +158,33 @@ void pm_state_exit_post_ops(enum pm_state state, uint8_t substate_id)
 	switch (state) {
 	case PM_STATE_SUSPEND_TO_IDLE:
 		if (substate_id <= 2) {
+			/* Erratum 2.2.15:
+			 * Enable ICACHE when exiting stop mode
+			 */
+			LL_ICACHE_SetMode(LL_ICACHE_1WAY);
+			LL_ICACHE_Enable();
+			while (LL_ICACHE_IsEnabled() == 0U) {
+			}
+
 			LL_LPM_DisableSleepOnExit();
 			LL_LPM_EnableSleep();
 		} else {
 			LOG_DBG("Unsupported power substate-id %u",
 							substate_id);
 		}
-	case PM_STATE_STANDBY:
+		break;
-		/* To be tested */
-		LL_LPM_EnableSleep();
 	case PM_STATE_SUSPEND_TO_RAM:
+#if defined(CONFIG_PM_S2RAM)
+		stm32wba_init();
+		stm32_power_init();
+
+		LL_LPM_DisableSleepOnExit();
+		LL_LPM_EnableSleep();
+#else
+		LOG_DBG("Suspend to RAM needs CONFIG_PM_S2RAM to be enabled");
+#endif
+		break;
+	case PM_STATE_STANDBY:
 		__fallthrough;
 	case PM_STATE_SUSPEND_TO_DISK:
 		__fallthrough;
@@ -141,6 +216,15 @@ static int stm32_power_init(void)
 
 	LL_AHB4_GRP1_EnableClock(LL_AHB4_GRP1_PERIPH_PWR);
 
+#ifdef CONFIG_DEBUG
+	LL_DBGMCU_EnableDBGStandbyMode();
+	LL_DBGMCU_APB7_GRP1_FreezePeriph(LL_DBGMCU_APB7_GRP1_RTC_STOP);
+	LL_DBGMCU_APB7_GRP1_FreezePeriph(LL_DBGMCU_APB7_GRP1_LPTIM1_STOP);
+#else
+	LL_DBGMCU_DisableDBGStandbyMode();
+#endif
+
+	/* Enabling  Ultra Low power mode */
 	LL_PWR_EnableUltraLowPowerMode();
 
 	LL_FLASH_EnableSleepPowerDown();

soc/arm/st_stm32/stm32wba/soc.c

@@ -32,7 +32,7 @@ LOG_MODULE_REGISTER(soc);
  *
  * @return 0
  */
-static int stm32wba_init(void)
+int stm32wba_init(void)
 {
 	/* Enable instruction cache in 1-way (direct mapped cache) */
 	LL_ICACHE_SetMode(LL_ICACHE_1WAY);
@@ -51,7 +51,6 @@ static int stm32wba_init(void)
 	LL_PWR_SetRegulatorSupply(LL_PWR_LDO_SUPPLY);
 #endif
 
-
 	return 0;
 }
 

soc/arm/st_stm32/stm32wba/soc.h

@@ -17,6 +17,9 @@
 
 #include <stm32wbaxx.h>
 
+/* function exported to the soc power.c */
+int stm32wba_init(void);
+
 #endif /* !_ASMLANGUAGE */
 
 #endif /* _STM32WBA_SOC_H_ */